Crimped terminal wire having a rubber plug, method for making same and tool for assembling same

Abstract: A rubber plug for sealing is engaged with a covered wire, and the rubber plug is prevented from being disconnected when an insulation barrel of a terminal fitting is clamped to the plug. The insulation barrel is curved and clamped along a maximum extent of the outer circumferential surface of the rubber plug, while both end portions of the insulation barrel are overlapped. Both ends of the insulation barrel can be prevented from biting onto the surface of the rubber plug.

Description: BACKGROUND OF THE INVENTION The present invention relates to a wire terminal connector, and more particularly, to a crimped terminal wire having a rubber plug. Conventionally, a thin insulated wire 30 having a rubber plug shown in Fig. 4 is inserted into a connector that is used in a place where water-proof capability is required. That is, a rubber plug 32 for sealing is engaged with a boundary portion of a core wire 31 of the thin insulated wire 30, so that a connecting portion between the insulated wire 30 and the wire insertion hole of a connector housing can be tightly sealed. In this connection, the rubber plug 32 is made of silicon rubber and formed into a cylindrical shape. After the rubber plug 32 has been inserted with the wire 30, it is prevented by the clamping or crimping action of a terminal fitting 33 from being disconnected. As shown in Figure 4, the conventional terminal fitting 33 includes a wire barrel 34 that clamps or crimps the core wire 31 and an insulation barrel 35 that clamps the rubber plug 32. Both ends of the insulation barrel 35 are separated and curved along an outer circumferential surface of the rubber plug 32 in the process of clamping. At this time, an appropriate crimping force is given to the insulation barrel 35, so that the rubber plug 32 is prevented from being disconnected. In the above crimping system, the insulation barrel 35 is crimped under the condition that both ends are butted against each other. Therefore, when a crimping force is applied to the insulation barrel, both ends bite onto a surface of the rubber plug 32. For this reason, the clamping portion of the rubber plug 32 may be cracked, which could cause the wire to be damaged or disconnected. Also, the same metal terminal fitting 33 is applied to a plurality of types of wires (rubber plugs) as long as the outer diameter is in a predetermined range. Therefore, it is difficult to provide a constant clamping force. In other words, when the outer diameter of the plug is small, the insulation barrel is too big. If the critical bending radius of the clamp pieces is larger than the radius of the rubber plug, the insulation barrel loses contact with the surface of the plug, since the ends of the insulation barrel cannot apply an adequate crimping force to the plug. When the other words, when the outer diameter of the plug is small, the insulation barrel is too big and the ends of the insulation barrel cannot apply an adequate crimping force to the plug (see Fig. 3). The critical bending radius of the clamp pieces 9a and 9b is larger than the diameter of the rubber plug, which causes the guide piece 9b (Fig. 3) to lose contact with the surface of the plug 3a. When the outer diameter of the plug is large, the insulation barrel is too small and the ends of the insulation barrel cut into the outer diameter of the plug (Figure 5). When a sufficient crimping force cannot be provided to the rubber plug 32 because of a mismatch between the sizes of the plug and the insulation barrel, a positional slippage is caused in the rubber plug 32 in the case where the thin insulated wire 30 is inserted into an insertion hole of the wire. When the insulation barrel 35 is clamped again, the working efficiency is remarkably decreased. The above problems are encountered in the crimping system of the prior art. In addition, the insulation barrel is crimped onto a member made of rubber, the resilience of which is high. Essentially, it is difficult to crimp the insulation barrel to the rubber plug because of the springiness of the resilient material. As a result, an unnecessarily high crimping force tends to be applied in an effort to make up for the insufficient crimping effect. Document US-A-4 832 616 discloses an electrical connector which corresponds substantially to the state of the art mentioned above and shown in Fig. 4. Document US-A-3 404 368 discloses an electrical connector with a ferrule member having a conductor-engaging section and an insultation-engaging section. The insulation-engaging section has overlapping surfaces with projections and openings which engages with each other. A stepped section for applying contact pressure onto the cable is provided. However, with this electrical connector cables of different sizes cannot be connected with the ferrule member efficiently. Document GB-A-650 096 relates to an electrical connector and a method for connecting a wire with the electrical connector. A crimper is used for crimping ears of a ferrule portion of the electrical connector. In GB-A-650 096 the crimping surfaces of the crimper are arranged in different planes. An overlapping of the ears of the ferrule portion does not occur. Document US-A-3 286 223 relates to a cylindrical ferrule as part of an electrical terminal. This ferrule is manufactured of a metal stamping by rolling it into a tuber over a wire conductor and by joining overlapped edge sections with a crimp. With such a crimp the wire conductor is considerably deformed for effecting the termination of the wire conductor in the ferrule. SUMMARY OF THE INVENTION The present invention has been achieved in the light of the above problems. It is an object of the present invention to provide a wire terminal connected to a wire that overcomes the shortcomings of the prior art in which a rubber plug can be securely fixed with an appropriate clamping level. The object of the present invention is solved by a wire terminal connected to a wire according to claim 1, a method for making such a wire terminal according to claim 6 and an assembly tool for such a wire terminal according to claim 8. Further developments of the invention are disclosed in the subclaims. According to the above construction, under the condition that the insulation barrel makes maximum contact with and is curved along an outer circumferential surface of the rubber plug, and both ends of the insulation barrel are overlapped, the insulation barrel is crimped to the rubber plug, so that the entire thin insulated wire can be prevented from being disconnected. According to the present invention, while both ends of the insulation barrel are overlapped, the rubber plug is clamped. Accordingly, both ends of the insulation barrel do not bite onto the surface of the rubber plug, so that an approximately uniform clamping force can be given onto the entire circumference of the rubber plug. With respect to wires of different diameters, the insulation barrel can be curved along the outer circumference of the rubber plug being maintained in a predetermined profile while changing the amount of overlap. Therefore, the same insulation ring can be applied to a plurality of types of wires (rubber plugs). BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be described in detail with reference to the following drawings wherein: Fig. 1 is a perspective view of the covered wire having a rubber plug of the present invention. Figs. 2(a)-2(c) are sectional views showing a sequential clamping operation of the insulation barrel. Fig. 3 is a sectional view showing the insulation barrel portion of the covered wire according to the present invention. Fig. 4 is a perspective view showing a conventional covered wire having a rubber plug. Fig. 5 is a sectional view showing an insulation barrel portion of the conventional covered wire. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Fig. 1 is a view showing an end portion of the thin insulated wire 1. The end portion of the thin covered wire 1 is peeled by a predetermined length so that a core wire 2 is exposed. A rubber plug 3 is provided just inside the portion where the thin covered wire is peeled. The rubber plug 3 is made of silicon or nitrile rubber, and the entire rubber plug 3 has a generally cylindrical shape. As illustrated in Figure 1, three sealing rings 4 of an end portion of the rubber plug 3 are provided at regular intervals in such a manner that the sealing rings 4 are successively protruded in an axial direction in a flange-like manner. In addition, a crimping portion 3a to be clamped by a terminal fitting 5 is provided. At a fore end of the terminal fitting 5, a contact portion 6 is provided for electrical connection. At an intermediate portion of the terminal fitting 5, a wire barrel 7 is provided for clamping or crimping the core wire 2. The wire barrel 7 is subjected to clamping deformation with respect to the core wire 2 by a well known crimping device. At a rear end of the terminal fitting 5, an insulation barrel 8 is provided. The insulation barrel 8 includes a pair of rising clamping pieces 9a and 9b, penetrating the crimping portion 3a of the rubber plug. In this case, the height of the clamping piece 9a and that of the clamping piece 9b are approximately the same. Then the insulation barrel 8 is overlapped and crimped by a crimper 10 described below. In this way, the insulation barrel 8 is clamped and fixed to the crimping portion 3a of the rubber plug 3. Clamping of the insulation barrel 8 is carried out following the sequential procedure shown in Figs. 2(a)-2(c). Prior to clamping of the insulation barrel 8, the thin covered wire is inserted into the rubber plug 3, and the wire barrel 7 of the terminal fitting 5 is clamped to the core wire 2. The insulation barrel 8 is put on an anvil 11, and the crimper 10 is lowered under this condition. At this time, the first and second curved crimping surfaces 12, 13, the depths or heights of which are different, are formed on the lower surface of the crimper 10. When the crimper 10 descends, an upper end of one clamping piece 9a first comes into contact with the skirt portion of the first crimping surface 12 before the other clamping piece 9b comes into contact with its associated skirt portion. The clamping piece 9a on the first side is bent or conformed onto the rubber plug 3 along the first crimping surface 12. At this point in assembly, however, the other clamping piece 9b still does not come into contact with the second crimping surface 13. When the crimper 10 further descends, the clamping piece 9b, which is on the non-contact side, comes into contact with the second crimping surface 13, so that the curving deformation is gradually started. In this connection, the anvil 11 is also moved upward synchronously with the descending motion of the crimper 10. When the crimper 10 further approaches the anvil 11 under the condition shown in Fig. 2(a), the fore end of the clamping piece 9a is further curved to the crimping portion 3a of the rubber plug 3, and the other clamping piece 9b is curved in such a manner that the clamping piece 9b is overlapped on the clamping piece 9a and any remaining exposed regions of the rubber plug (shown in Fig. 2(b)). When the clamping operation advances to a condition shown in Fig. 2(c), the entire clamping piece 9a is curved and makes contact with the outer circumferential surface of the crimping portion 3a, and the other clamping piece 9b is overlapped on the clamping piece 9a in a predetermined range. The range and overlap depends on the size of the wire and rubber plug. Under this condition, the clamping pieces 9a, 9b are given a pressing force by the crimper 10 and anvil 11. Accordingly, both clamping pieces 9a, 9b are overlapped depending on the size of the rubber plug, so that both end portions of the clamping pieces 9a, 9b are shifted from a center line on which a pressing force is acted. Consequently, the edge portions of the clamping pieces do not bite into the rubber plug as in the related art (Fig. 5), so that the crimping portion 3a of the rubber plug 3 is not damaged. With respect to various wire diameters, an approximately constant fastening condition can be realized only when an amount of overlap is changed. When crimping variably sized diameter wires, however, the first and second pieces, in varying proportions, maintain contact with a maximum degree of the surface of the variable diameter rubber plug. The critical radius of the combined guide pieces always matches the (variable) radius of the rubber plug to maximize the holding function. Consequently, a stable clamping force can be provided because the frictional contact is maximized between the rubber plug and the clamping pieces. While the invention has been described in detail with reference to preferred embodiments thereof, which are intended to be illustrative but not limiting, various changes may be made without departing from the scope of the invention. For example, in order to suppress the edge biting action, both end edges of the clamping pieces 9a, 9b may be chamfered (Figs. 2(a)-(c)), and further the side edges may be chamfered. In order to further suppress the edge biting action, the clamping pieces 9a, 9b may also be folded outside.

Claims: A wire terminal connected to a wire (1) comprising: a terminal fitting (5); a wire barrel (7), coupled to said terminal fitting (5), and adapted to clamp an exposed region (2) of said wire (1); a rubber plug (3) having a through-bore providing a passage for an end of said wire (1), said plug (3) having a crimping portion (3a); and an insulation barrel (8), including first and second clamping arms (9a, 9b) that are crimped onto an outer circumferential surface of said rubber plug (3), said insulation barrel (8) being curved along said outer circumferential surface, characterized in that the first arm (9a) being overlapped with respect to the second arm (9b), and the second arm (9b) comprises in the connected state of the first and second arms and the rubber plug a substantially straight portion which is arranged substantially in the direction of a center line on which a pressing force was applied when the arms were crimped onto the outer circumferential surface of said rubber plug (3), so that the first arm (9a) and the second arm (9b) accommodate wires (1) having various diameters while maintaining a tight frictional grip with a maximum degree of contact between the surfaces of the first and second arms (9a,9b) and the rubber plug (3). The wire terminal of claim 1, wherein the first and second clamping arms (9a,9b) are of different lengths so that the first and second clamping arms (9a,9b) are shifted from a center line on which a pressing force is applied. The wire terminal of claim 1 or 2, wherein the first and second clamping arms (9a,9b) have respective surfaces that, combined, make contact with substantially an entire perimeter of said rubber plug (3). The wire terminal of one of the preceding claims, wherein the first and second arms (9a, 9b) comprise a permanently deformable material. The wire terminal of one of the preceding claim, wherein the first and second arms (9a,9b) have chamfered ends. A method for making a wire terminal according to claim 1, the method comprising the steps of: providing the insulating barrel (8) with the first clamping arm (9a) and the second clamping arm (9b); placing the crimping portion (3a) of the rubber plug (3) between the first and second arms (9a,9b); bending and conforming the first arm (9a) to the shape of the crimping portion (3a) including engaging a first end of the first arm (9a) with a first tool surface (12) of a tool (10); holding an end portion of the second clamping arm (9b) of the wire terminal during part of the movement of said tool (10) toward the wire terminal at an edge (14) between the first inner surface (12) and a second inner surface (13) ; bending and conforming the second arm (9b) to the shape of the first arm (9a) and the crimping portion (3a) including sequentially engaging a second end of the second arm (9b) with the second tool surface (13) of said tool (10); and permanently deforming the first and second arms (9a, 9b so that the first and second arms (9a 9b) are maintained substantially in contact with the crimping portion (3a) . The method of claim 6, further comprising the step of chamfering ends of the first and second arms (9a, 9b) to prevent the ends from biting into the crimping portion (3a) and to allow the first and second arms (9a,9b) to slide with respect to one another during the bending steps. An assembly tool for a wire terminal according to claim 1 comprising a main body (10) having a generally bell-shaped cross-section including a first arm and a second arm, the first and second arms having respective inner surfaces (12, 13), wherein the inner surfaces (12, 13) have different depths, i.e. the distance between the topmost portion and the lowermost portion of the second inner surface (13) is larger than the distance between the topmost portion and the lowermost portion of the first inner surface (12); and an edge (14) between the first inner surface (12) and the second inner surface (13) for holding an end portion of a second clamping arm (9b) of the wire terminal during part of the movement of the assembly tool toward the wire terminal. The assembly tool of claim 8, wherein the first inner surface (12) is adapted to engage the insulating barrel (8) before the second inner surface (13) engages the insulating barrel (8) so that first and second clamping arms (9a,9b) of said wire terminal are overlapped and shifted from a center line on which a tool pressing force is applied. The assembly tool of claim 8 or 9, further comprising an anvil (11) having a cradle shape for holding the wire terminal stationary during assembly.

Inventors: NABESHIMA AKIRA, NABESHIMA, AKIRA, NABESHIMA, AKIRA, C/O SUMITOMO WIRING SYST., LTD.
Applicants: SUMITOMO WIRING SYSTEMS, SUMITOMO WIRING SYSTEMS, LTD.
Application year: 1994
Main classification: H01R13
IPC codes: H01R13, H01R4, H01R43